Method and device for welding rails with heat treated head using separate alloy additives

ABSTRACT

In a method and device for welding rails with a heat treated head, the halves of a casting mold made from a refractory material having at least one lateral vent are mounted around two end pieces of the rail that are to be connected, thereby forming a casting space. The mounting mold is preheated and the casting space is sealed by a sealing element made of refractory material covering the rail head; steel produced by a metallothermal process penetrates into the casting space after passing over the sealing element and fills the space, whereby alloy inserts in solid and compact form arranged above the rail head in the casting space are contacted with part of the steel forming the weld in the head zone.

The invention relates first to a method for welding rails with a heattreated head, in which the halves of a casting mold made from arefractory material having at least one lateral vent are mounted aroundtwo end pieces of the rail that are to be connected, thereby forming acasting space. The mounting mold is preheated and the casting space issealed by a sealing element made of refractory material covering therail head; steel produced by a metallothermal process penetrates intothe casting space after passing over the sealing element and fills thespace, whereby alloy additives in solid and compact form arranged abovethe rail head in the casting space are contacted with part of the steelforming the weld in the head zone.

DE 196 37 283 A1 discloses a method for aluminothermal intermediatecasting welding of rails, whereby the aluminothermally produced steel iscast in a refractory casting mold which has an overflow and whichsurrounds the rail ends to be connected and alloy additives in a solid,compact form are brought into contact with a part of the steel runningout from the reaction crucible, which forms the welding in the rail headregion. In this manner, the alloy additives are arranged on a moldelement (sealing element) mounted on a header in the upper region of thecasting mold and covering the rail head. After completion of thealuminothermal reaction and separation of the steel from the slagaccording to requirements of a falling or rising casting, respectively,with falling or top casting with the latter or with rising or bottomcasting with the former, steel flowing out of the reaction crucible isalloyed, whereby the overflow is closed. In other words, an overflow(bypass) is not provided and the alloy additives are disposed on theheader and are first inserted into the mold after the preheating. Themolds used in the known methods indeed have lateral vents, however, noinlet channels separated from the casting space. With top casting, thesteel flows freely over the edges of the header into the upper part ofthe casting space; with a bottom casting, the steel running off from theheader flows first into the flow gate and ascends then from below intothe casting space.

It is an object of the present invention to provide a method of theabove-described type, in which the alloying can take place in the headregion by locating the alloy additives on the sealing element or headerand a selective flow of the alloy region of the casting space can occur.

This object is solved in that before preheating, an alloy insert with ashape that enables the preheating of the rail ends is placed in the moldand the metallothermally, in particular aluminothermally, producedsteel, after passing over the sealing element, penetrates into thecasting space through sprues provided in each half mold and emerges intothe casting space substantially in the area of the rail head.

By the separation of the alloy additives from the header or sealingelement, they can be integrated into the mold during or directly afterassembly. In addition, it is advantageous that they do not interferewith preheating after the integration. The sprues and their associationto the head region provide a selective filling of the bar and footregion of the casting mold on the one hand and of the casting spacesection associated with the head region to be alloyed on the other hand.

The invention also relates to a device for welding rails with a heattreated head, in particular according to the method of claim 1, with acasting mold comprising two mold halves made of a refractory material,each having at least one lateral vent, which define a casting space uponassembly around the two rail ends to be connected, with a sealingelement covering the rail head and closing the casting space and withalloy additives in a solid, compact form arranged above the rail head.

With the device of the present invention, it is provided that in bothmold haves in the area of the casting space above the rail head, abearing is provided, on which an alloy insert, having a shape thatenables preheating of the rail ends to be connected, can be placed andthat in each mold half, at least one sprue is provided, which opens inthe region of the rail head into the casting space.

The dependent claims 3-10 are directed to advantageous embodiments ofthe device of the present invention.

The invention will be described next in greater detail with reference tothe accompanying figures. In the drawings:

FIG. 1 shows a vertical section through a mold with a bearing grooveabove the rail head with a casting space tapering into the upper regionwithout a bypass;

FIG. 2 shows a vertical section through a mold comparable to FIG. 1 witha thinner alloy insert in the bearing groove and with a bypass betweenthe sprues and the lateral vents;

FIG. 3 shows a vertical section through a mold with a bearing step abovethe rail head with a casting space that does not taper into the upperregion with a bypass between the sprues and the foot flanks;

FIG. 4 shows a horizontal section through FIGS. 1-3 along the line IV-IVthrough a mold, in which the casting space has a rectangular crosssection at least in the region of the bearing and thereabove; and

FIG. 5 shows a horizontal section through FIGS. 1-3 along line IV-IVthrough a mold, in which the casting space has a circular cross sectionat least in the region of the bearing and thereabove.

With the device shown in FIG. 1, two mold halves 1, 2 are mounted aroundthe rail S with head K, bar S and foot F and define a casting space Gsurrounding the rail ends. The casting space G has a section G1 taperingout from the rail head K with a rectangular cross section (see FIG. 4),in which a circumferential bearing or support groove 3 is formed. Duringmounting of the two mold halves, a quadrilateral alloy insert 4 adaptedto the dimensions of the groove and with a central opening 4 a is placedin the bearing groove 3.

Sprues 5 are provided in the mold halves laterally near the section G1,which open to the lower end of the section G1 essentially in the area ofthe railhead K, and in the preferred manner, to the transition of thehead to the bar S of the rails.

The upper ends of the sprues open to a distribution space 6 to whichalso the section G1 opens. The opening of the section G1 to thedistribution space 6 can be closed by a bar-like sealing or closureelement 7 having an engagement section 7 a when the rail ends are to bepreheated by means of a burner through the opening. The alloy insert 4,then, is inserted independently from the sealing element 7 into the moldand is preheated with the mold.

During the welding of the rails, steel contacting the sealing element 6is distributed in the distribution space and flows from above into thesprues.

Provided in each of the mold halves is a lateral vent 8, which is placedessentially on the ends of the flanks of the foot F on the casting spaceG. The outlet opening of the lateral vent 8 lies above the inlet openingof the sprue 5.

With the embodiment of FIG. 2, a thinner alloy insert 4 a is placed inthe groove 3. This shows that an adaptation is possible depending on thedesired head hardness.

In addition, a bypass 9 to the associated lateral vent 8 is provided atthe lower end of the sprue 5. The bypass is represented with ahorizontal gradient. However, it also can run diagonally or morevertically. This is also true for bypasses, which can be provided inaddition to the one.

With the embodiment of FIG. 3, a step 10 is provided in section G1′ asthe bearing or support. Above the step 10, the section G1′ has aconstant cross section, so that the alloy insert 4 also can be placedaround the rails after assembly of the two mold halves.

In addition, a bypass 11 to the casting space G is provided at the lowerend of the sprue 5 in the area of the flanks of the rail foot F. Thebypass is represented with a vertical gradient. It also can have adiagonal orientation. This is true also for bypasses, which can beprovided in addition to the one.

The structure of the bearing can be exchanged in FIGS. 2 and 3. Undercertain conditions, also a combination of the bypasses 9 and 11 iscontemplated.

FIG. 4 shows with dotted lines that also individual bars 4′ can be usedas alloy inserts instead of the one-piece, quadrilateral plate 4 withthe central opening 4a. The individual bars 4′ are placed in the groove,such that they do not impair preheating.

FIG. 5 shows a circular cross section of the casting space above therail head in the area of the bearing in the form of the groove 3 or thestep 9. A circular ring or circular ring parts that do not necessarilyform a complete circle can be used as the alloy insert 12 (see parts 12′in FIG. 5). For adapting to the head curing, it is also contemplatedthat multiple circular rings can be placed over one another with theembodiment of the bearing as a step after assembly of the mold halves.

The invention thus offers the possibility for adapting to different headcuring jobs with one or multi-part alloy inserts or with multipleone-part alloy inserts, whereby the alloy inserts or alloy insert partsalso can have a different configuration.

1-10. (canceled)
 11. A method for welding rails with heat-treated heads,comprising the following step: providing a casting mold made of arefractory material and having two mold halves, wherein each mold halfhas at least one lateral vent and at least one sprue; mounting the twomold halves around two end pieces of the rail that are to be connected,thereby forming a casting space; inserting an alloy insert into thecasting mold, wherein the alloy insert has a shape that enables topreheating of the end pieces of the rail; preheating the mounting mold;sealing the casting space with a sealing element made of refractorymaterial covering the rail head; introducing steel produced by ametallothermal process into the casting space through the sprues in themold halves after passing over the sealing element, thereby filling thecasting space, wherein said steel emerges into the casting spacesubstantially at the rail head; and contacting alloy inserts in solidand compact form arranged above the rail head in the casting space withpart of the steel forming a weld in a region of the rail head.
 12. Adevice for welding rails with heat treaded heads, comprising: a castingmold comprising two mold halves made from a refractory material eachhaving at least one lateral vent, wherein said two mold halves, uponassembly around two rails ends that are to be connected, define acasting space; a sealing element covering the rail head and sealing thecasting space; alloy inserts in solid and compact form arranged abovethe rail head, wherein in both mold halves in an area of the castingspace above the rail head, a bearing is provided, wherein an alloyinsert with a shape making it possible to preheat end pieces of the railcan be placed on the bearing, and wherein in each mold half, at leastone sprue is provided, wherein the at least one sprue opens in a regionof the rail head into the casting space.
 13. The device of claim 12,wherein the bearing is formed by a circumferential groove, such that thealloy insert can be inserted during the mold assembly
 14. The device ofclaim 12, wherein the bearing is formed by a circumferential step, suchthat the alloy insert can be inserted after the mold assembly.
 15. Thedevice of claim 12, wherein the casting space has a quadratic crosssection at least in the area of the bearing, and wherein the alloyinsert comprises at least one bar.
 16. The device of claim 12, whereinthe alloy insert comprises at least one quadrilateral element with acentral opening.
 17. The device of claim 12, wherein the casting spacehas a circular cross section at least in the area of the bearing, andwherein the alloy insert comprises at least one graduated ring.
 18. Thedevice of claim 17, wherein the alloy insert comprises a circular ring.19. The device of claim 12, wherein each mold half has at least onebypass from the sprue to the lateral vent.
 20. The device of claim 12,wherein each mold half has at least one bypass from the sprue to thecasting space in the region offoot flanks of the rails.